1*4882a593Smuzhiyun /* SPDX-License-Identifier: GPL-2.0-or-later */ 2*4882a593Smuzhiyun /* Count leading and trailing zeros functions 3*4882a593Smuzhiyun * 4*4882a593Smuzhiyun * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. 5*4882a593Smuzhiyun * Written by David Howells (dhowells@redhat.com) 6*4882a593Smuzhiyun */ 7*4882a593Smuzhiyun 8*4882a593Smuzhiyun #ifndef _LINUX_BITOPS_COUNT_ZEROS_H_ 9*4882a593Smuzhiyun #define _LINUX_BITOPS_COUNT_ZEROS_H_ 10*4882a593Smuzhiyun 11*4882a593Smuzhiyun #include <asm/bitops.h> 12*4882a593Smuzhiyun 13*4882a593Smuzhiyun /** 14*4882a593Smuzhiyun * count_leading_zeros - Count the number of zeros from the MSB back 15*4882a593Smuzhiyun * @x: The value 16*4882a593Smuzhiyun * 17*4882a593Smuzhiyun * Count the number of leading zeros from the MSB going towards the LSB in @x. 18*4882a593Smuzhiyun * 19*4882a593Smuzhiyun * If the MSB of @x is set, the result is 0. 20*4882a593Smuzhiyun * If only the LSB of @x is set, then the result is BITS_PER_LONG-1. 21*4882a593Smuzhiyun * If @x is 0 then the result is COUNT_LEADING_ZEROS_0. 22*4882a593Smuzhiyun */ count_leading_zeros(unsigned long x)23*4882a593Smuzhiyunstatic inline int count_leading_zeros(unsigned long x) 24*4882a593Smuzhiyun { 25*4882a593Smuzhiyun if (sizeof(x) == 4) 26*4882a593Smuzhiyun return BITS_PER_LONG - fls(x); 27*4882a593Smuzhiyun else 28*4882a593Smuzhiyun return BITS_PER_LONG - fls64(x); 29*4882a593Smuzhiyun } 30*4882a593Smuzhiyun 31*4882a593Smuzhiyun #define COUNT_LEADING_ZEROS_0 BITS_PER_LONG 32*4882a593Smuzhiyun 33*4882a593Smuzhiyun /** 34*4882a593Smuzhiyun * count_trailing_zeros - Count the number of zeros from the LSB forwards 35*4882a593Smuzhiyun * @x: The value 36*4882a593Smuzhiyun * 37*4882a593Smuzhiyun * Count the number of trailing zeros from the LSB going towards the MSB in @x. 38*4882a593Smuzhiyun * 39*4882a593Smuzhiyun * If the LSB of @x is set, the result is 0. 40*4882a593Smuzhiyun * If only the MSB of @x is set, then the result is BITS_PER_LONG-1. 41*4882a593Smuzhiyun * If @x is 0 then the result is COUNT_TRAILING_ZEROS_0. 42*4882a593Smuzhiyun */ count_trailing_zeros(unsigned long x)43*4882a593Smuzhiyunstatic inline int count_trailing_zeros(unsigned long x) 44*4882a593Smuzhiyun { 45*4882a593Smuzhiyun #define COUNT_TRAILING_ZEROS_0 (-1) 46*4882a593Smuzhiyun 47*4882a593Smuzhiyun if (sizeof(x) == 4) 48*4882a593Smuzhiyun return ffs(x); 49*4882a593Smuzhiyun else 50*4882a593Smuzhiyun return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0; 51*4882a593Smuzhiyun } 52*4882a593Smuzhiyun 53*4882a593Smuzhiyun #endif /* _LINUX_BITOPS_COUNT_ZEROS_H_ */ 54